Heat Pumps, Carbon Emmissions, and Carbon Dioxide: a Love Story.

I love heat pumps. The refrigeration cycle is an elegant and beautiful thermodynamics hack: by manipulating the temperature and pressure of a gas/liquid phase changing fluid, heat can be forced to move from a cold space to a warmer one. A neat trick on it's own, but better is the fact that the energy required to drive this process is significantly less than the energy that is actually moved - by a ratio of up to 6:1.

Best is the fact that the energy used to drive the cycle (which turns into heat via friction and ends up being picked up by the phase change fluid) is itself transferred to the high temperature zone. So in contrast to a fossil fuel heater, where 81% - 97% (at the very most) of the energy available in the fuel is transferred to the heated space, a heat pump moves between 200%-400% more energy than it uses in electricity.

However, heat pumps use 'freons' - the outlawed CFCs like R22, and the new HCFCs like R410A or R404A -- and these gases are expensive, were ozone depleting, and cause climate change. Furthermore, commercial HCFC heat pumps have historically been limited to outputs of 55C - considered due to bacterial growth dangers to be to low for domestic hot water use.

However, there is good news: one of the up and coming heroes of the refrigerant world is the world's leading climate changing gas.

Carbon dioxide (CO2) in the atmosphere causes climate change, and it is released in large volumes due to our civilization's fossil fuel addition. It's important to remember that carbon dioxide emissions resulting from disruption of natural carbon sinks is harmful to the planet's atmospheric carbon dioxide levels, but in previously occurring quantities of atmospheric CO2 (prior to about 200 years ago) this life-giving gas formed (and still forms) the building block plants use, in combination with water and sunlight, to grow.

CFC refrigerants, on the other hand, are synthetic chemicals with no origin or purpose in nature. I'm not intrinsically opposed to such chemicals unless they have negative properties - but CFCs, and HCFCs, the environmentally preferable replacements which do not cause ozone layer depletion - cause global warming at a rate 1500 - 4100 times the rate of an equivalent volume of CO2. And because refrigeration cycles require that the CFCs function in a high pressure environment and in a cost-effective piping system, even factory sealed systems can lose their refrigerant charge over time. In large grocery refrigeration systems, leakage rates of 5%-15% are not uncommon.

This environmental consideration, along with the very high cost of HCFC gas - is driving a current industry quest for cost effective refrigeration solutions utilizing natural refrigerants - that is, non-synthetic, naturally occurring chemicals which have phase changes from gas to liquid at temperatures and pressures suitable for food refrigeration or space conditioning.

Ironically enough, CO2, the 'problem' greenhouse gas, turns out to be a fantastic refrigerant. Here are some of the best features about CO2 refrigeration systems:

• low material costs in comparison to HCFCs, due to a high heat of vaporization, which allows lower mass flow rates through the system, and smaller tubing.
• the phase change properties of CO2 are such that much hotter condensing temperatures can be achieved in CO2 systems: products available in the marketplace today can heat water to 60C - 90C, while still operating with a coefficient of performance of up to 4.
• in some systems, this high output temperature can be created concurrently with very low evaporation temperatures; in fact, COPs increase with higher temperature differences between the low and high sides of the system. This is very unusual and creates opportunities for heat pumps where they would typically be unable to perform.
• very inexpensive: CO2 costs between .80c - $2.00/lb, versus $22-$30/lb for HCFCs.
• available: CO2 is used in the food industry to carbonize fountain drinks; easily purchased in large quantities anywhere in North America where fast food can be found.
  
  Japan's in this secret. Over the last 10 years, over 1.5 million 'EcoCute' heat pump domestic hot water heaters have been sold to homes throughout the country. These units cost 66% less to operate than an electric water heater. More information can be found at http://en.wikipedia.org/wiki/EcoCute.
  
  The only caveat to this love-in for heat pumps is that, depending on what electrical grid the heat pump is supplied by, the overall climate change impact of it's operation will change dramatically - and isn't always a win over a natural gas appliance.
  
  In Alberta, Canada, most electricity is generated by burning fossil fuels like natural gas in remote power plants to generate heat, and produce steam. This steam runs a turbine, which generates electricity (30-45% efficient process). This electricity is run through high voltage wires (7-8% line losses), through several step down transformers (each of which has 1-5% losses). Even with a COP of 3, it's probably better just generate the heat on site (3%-20% losses) than to bother with this.
  
  However, for many other grids, such as next door neighbour British Columbia, much of the electrical generation is sources from hydro, wind, and nuclear power. Without fossil fuel origins, there are only secondary environmental impact greenhouse gas emissions (i.e. methane from flooded lands for hydro) and line losses. The use of electricity to pull heat from surroundings and use it effectively makes sense for these areas, and supports the development of clean alternative electricity sources.

Building Benchmarking: getting started is the hardest part.

'Benchmarking' is the only way that organizations or individuals trying to measure the energy savings their hard won retrofits or new energy efficient buildings have created, and demonstrate them to a larger world.

This important exercise can also help demonstrate to stakeholders how the organizations facilities are faring as compared to the competition's buildings, or even how buildings within a single organization compare to each other.

Over the long term, access to this information helps the facility manager develop an energy use awareness - an internal sense of how much energy makes sense for a given building to use, and how much money to expect to pay for energy in a poorly insulated rental or purchase property.

Energy labelling of buildings is one suggested way of creating this awareness. ASHRAE has created Building EQ, a program which would label buildings anywhere from net-zero energy to unsatisfactory, both as designed and as operated, and provide owners an easy means of comparing buildings to each other. ASHRAE's Fundamentals textbook, published every 4 years, also has a upper, median, and lower quartile energy performance data for a variety of building types.

Energy Star is much more established program that allows building owners to compare their buildings to all other buildings of their type registered in the program, and, solely on the basis of energy bills per square foot (adjusted for occupancy and certain other factors) learn where their building ranks. The top 25% of buildings rate as 'Energy STAR' rated. The wonderful thing about this program is that the target moves with the industry: as better buildings are built and registered, the standard moves and helps move your organization along with it to maintain certification.

Lawrence Berkeley National Labs also has a fabulous program, Energy IQ, wherein a large quantity of detailed energy data can be accessed and sorted or screened according to building vintage, exact occupancy type, and more. A larger range of building types are available in this program as compared to Energy Star's database.

In addition to benchmarking a building against other buildings, it's advisable and often fruitful to benchmark a building against itself. By choosing a reference year (if your building is that old, 1990 has the benefit of being the Kyoto treaty reference year) and continuing to benchmark your building against that one year, the effect of internal retrofits and occupant behavioural changes can be demonstrated in an easy to understand way.

When implementing occupant behaviour change campaigns, logging and providing to staff ongoing progress statements - especially if one building can be pitted against another -- can help foster healthy competition and a sense of pride in the achievements of the organization and of teams within it.

I hope that energy benchmarking becomes a part of your month-to-month energy management routine, and can provide an ongoing value with performance feedback and growth.